Tests for determining processing parameters and/or control parameters are required on laser processing machines in the manufacturer's development, training and demonstration departments, in after-sales service or also by the customer, since those parameters may vary greatly depending on the chosen processing task.
For example, a wide variety of materials may be processed with a laser processing machine, such as structural steel (uncoated, electroplated or hot-dip galvanised), stainless steel or aluminum. Depending on the material and the thickness of the workpiece to be processed, in the case of laser cutting, for example, different cutting methods are employed (oxygen cutting, nitrogen high-pressure cutting, nitrogen, oxygen or compressed air high-speed cutting, compressed air cutting or plasma-assisted cutting). Depending on the material, workpiece thickness and cutting method, a wide variety of technological constraints have to be taken into consideration, for example piercing and approach methods, geometric limit values during approach and, in the case of contour sizes, minimum rounding radii or spacing from neighboring parts. Furthermore, laser cutting machines may be equipped with lasers of differing output power.
Reliable and high-quality processing results can be achieved only if careful consideration is given to the constraints which vary according to type of material, thickness of material and cutting method. To control the processing of materials with a laser cutting machine, while taking into consideration the constraints that are to be observed, it is therefore necessary for various parameter data sets to be known or to be determined for every type of laser. Such a data set typically consists of processing parameters and control parameters. The processing parameters include, for example, focus position, laser output power, gas pressure and speed of movement, and comprise (numerical) values for reliable piercing, cutting of different contour sizes, labeling, point marking, ablating and welding. The control parameters define, in dependence on the processing that is to be performed, what is to be done under what conditions, that is to say, what processing parameters are to be called up in the control program and what geometric constraints (e.g. approach lengths in dependence on workpiece thickness, necessary rounding radii at corners of the contour, minimum permissible contours, . . . ) are to be observed.
In determining or verifying such data sets for controlling the laser processing of materials, the following tasks arise: determining and optimizing suitable processing parameters (e.g. focus position, cutting gas pressure, laser output power, pulse frequency, . . . ) for various types of processing such as piercing, cutting, labeling, point marking, ablating, welding taking the control parameters into consideration, determining control parameters, validating the processing parameters and control parameters for the various types of processing in continuous machine operation, and producing near-production test pieces using the processing parameters for the various types of processing. That procedure must ensure before production, i.e. even before the processing operation, that the interaction of the available processing parameters, the material to be processed and the state of the machine makes reliable processing possible.
The tasks mentioned are usually carried out by machine operators who, on the basis of their experience, create suitable test programs which are then executed by the laser processing machine. For each task and for each material to be processed, a suitable control program is programmed for the purpose. That procedure is very time-consuming, and a standardized procedure on the part of different operators can be ensured only with a great deal of documentation and information-gathering work.
JP 04070908 A provides an automatic programming device for a laser processing machine, in which a knowledge database is provided in which expert knowledge on laser processing is stored. With the aid of the expert knowledge a decision function determines the optimum processing parameters, which are passed to a function to create an NC program. The knowledge database can be filled with expert knowledge by an operator by way of a dialogue function.
A method and an apparatus are known from JP 2002239760 A, in which optimum processing parameters are determined by experimentally specifying processing parameters with the exception of a processing speed. With constant processing parameters, the processing speed is then varied in order to determine the range of values of the processing speeds that are possible with those processing parameters. That procedure is repeated, with the processing parameters being changed, until the optimum processing parameters are found, at which the range of values of the processing speeds available for the processing operation is at a maximum.
A programming method is known from JP 07001286 A, in which an operator is provided with a selection function for selecting a combination of input values that are characteristic of a processing operation. On the basis of those input values, for example the type of processing, an automatic decision is made as to the optimum processing parameters of the processing operation with the aid of parameter data sets.
JP 03230878 A provides a method and an apparatus for automatically specifying output conditions of a laser beam, for example its output power and pulse frequency, and for specifying the gas pressure of a stream of gas assisting the laser processing. For that purpose, parameter values such as type of material and thickness of material are read out from an NC processing program and an associated parameter data set is determined. The output conditions and the gas pressure for the laser processing operation are then determined from the parameter data set in dependence on a processing speed which is likewise read out from the NC processing program.